Process of preparing a puffed cereal product and the resulting product



United States Patent PROCESS OF PREPARING A PUFFED CEREAL PRODUCT AND THE RESULTING PRODUCT Louis J. Huber, Minneapolis, Minn., assignor to General Mills, Inc., a corporation of Delaware No Drawing. Application March 29, 1952, Serial No. 279,447

8 Claims. (Cl. 99-81) The present invention relates to a novel puffed product and to a process of producing the same. More particularly the invention relates to a puffed cereal product derived from a cooked starch-containing dough.

Pufied cereals of a wide variety have been prepared heretofore. They have been puffed by two processes principally; (1) the explosive pufiing resulting from the use of the puffing gun; and (2) putting by means of radiant heat. The explosive pufiing process involves the use of a pufling gun in which the material to be puffed is heated to a relatively high temperature under considerable pressure. The pulling gun is then suddenly opened and the material discharged to atmosphere, resulting in the explosive pufiing of the cereal material. Explosive pufiing is an expensive operation. The equipment employed must by built to resist high pressures. In addition, maintenance costs are high since the equipment is subjected to excessive stresses during the puffing operation. Furthermore, the material being puffed is subjected to elevated temperatures for fairly extensive periods of time, for example, from 3 to 6 minutes, and accordingly some of the nutritional values may be impaired by this extended elevated temperature treatment.

In the radiant putting process the material to be puffed is subjected to heat of a radiant nature. With most materials the degree of putting obtained by the radiant process is materially less than that obtained by the explosive pufiing process. Most materials do not puff to a satisfactory volume by the radiant process, and accordingly this process is employed for only a few materials which are found to puff to a reasonable volume by this method. In addition to the low volume obtained by the radiant process, frequently the puffed materials do not have the desirable eating characteristics such as tenderness, and the like, which are desirable in a product of this nature.

It has now been found possible to pufl cooked starchcontaining dough material by subjecting the material at a pufling moisture content to pressure between rolls heated to an elevated temperature. The material pufls to a large volume, frequently to a volume larger than that obtainable by the usual explosive puffing process. In addition, the physical characteristics of the puffed material are distinctly different from the physical characteristics of puflfed material produced by any other process. Moreover, the time during which the material is subjected to an elevated temperature is extremely small, of the order of a small fraction of a second. There is, therefore, relatively little adverse effect on the nutritional characteristics of the material. Furthermore, the equipment employed is simple and inexpensive and requires relatively little maintenance.

A further advantage is the fact that the present process permits the attainment of definite shapes in the finished product. For example, if it is desired to produce a thin puffed sheet, it can readily be obtained by this process. With other pufling processes, particularly the explosive process, thin sheets are likely to disintegrate into small particles and powder. With any of the other putfing processes, there is no means of controlling the characteristics of the surface since the expansion occurs on freely exposed surfaces not controlled by any positive shaping means. In the present process, however, since the material is in positive contact with the puffing rolls at the time of pufiing, the puffing rolls control the shape of the puffed product. By the employment of a specially shapeid roll, products having special shapes may be obtaine It is therefore an object of the present invention to provide a novel process of putting cooked starch-containing dough material.

It is another object of the invention to provide a novel puffed product produced by the above process.

The invention is applicable to any cooked starch-containing dough, and is particularly applicable to cereal doughs. The process is particularly adapted to the production of food products such as breakfast cereal snacks etc. but is also adapted to the production of any puffed starch-containing product whether of an edible nature or not. The cereal grains most commonly employed in the preparation of ready-to-eat cereals are com, oats, wheat and rice. These cereal grains are readily adapted to the present process. A wide variety of other cereal materials may also be employed. These include rye, barley, sorghum, and buckwheat. In addition other starchy materials may be employed, such as tapioca, mandioca, arrowroot, and sago. These materials may be introduced into the dough in the form of finely ground powders or flours, as meals, or in other forms. In place of whole grain materials selected fractions of these respective grains may be employed. For example, selected flours, meals, farina, bran, and the like may be employed, either alone or along with other starch-containing materials. Malted cereal grains may be employed also.

The starchy materials may be employed alone or in admixture with other materials such as salt, sugar, cocoa, honey, milk, molasses, cheese, yeast and the like.

The starchy material, either with or without the added material, is formed into a dough with water, and the dough is cooked to gelatinize the starch. Any method of cooking may be employed, but usually it is desirable to mix the dough in a jacketed mixer and cook the dough therein until the dough has acquired the proper degree of gelatinization for the production of a desirable puffed product. The particular time of cooking depends upon the material being treated, the temperature employed, and the type of equipment. In general it has been found that cooking of from 1 to 2 hours in a jacketed vessel heated with steam at 20 pounds per square inch has been found satisfactory. Commercial equipment to perform the cooking operation under these conditions is readily available. Considerable variation is possible in the quantity of water employed during the cooking operation. The minimum quantity of water which may be employed is that which will actually form a dough. Usually at least about 20-40% of moisture based on the weight of the dough is present at the time of cooking. Much larger quantities of moisture may be employed, but since this moisture must be removed prior to putting, the use of excess moisture is not desirable. Ordinarily a moisture content within the range of 3035% of the dough has been found desirable.

After the dough has been cooked it is shaped into any desired form for pufling. The dough may be sheeted into either large or small sheets and the sheets run through the pufiing rolls to produce a puffed sheet. The material may be formed into strips or small pellets. For the preparation of small pellets the dough may be extruded in a wide variety of equipment and the extruded material cut off in the form of small pellets. The size and shape of the material formed from the dough depends upon the nature of the product desired. For the preparation of a snack type of product, it may be desirable to form the material into strips or flakes of the size of crackers. For ready-to-eat breakfast cereals it is usually desirable to form the dough into small pellets which will puff into the size of pieces conventionally employed for ready-to-eat breakfast cereals. Doughs having the moisture content previously described usually can be shaped without any adjustment of the moisture content.

Prior to pufiing, the dough particles should be adjusted to a suitable puffing moisture. Generally a moisture content within the approximate range of 8-18% is suitable for this purpose. This moisture content during pufling is considerably less critical than it is in the gunpuffing operation. For most materials a moisture content of -15 is suitable. A moisture content of about 13.5% has been found highly satisfactory for most materials. The particular moisture content depends to some extent upon the nature of the material and accordingly the optimum moisture content can readily be determined for any given material. In general it may be stated that moisture contents outside the range specified above tend to give lower volumes. In addition, at the higher moisure levels there is a tendency for the product to have a pale uncooked and untoasted appearance. At the lower moisture levels there is less plasticity and accordingly a less clearly defined shape.

The puffing operation involves the step of feeding the cooked dough pieces to a pair of rolls heated to a temperature within the approximate range of 350-800% F. For most materials the preferred range of 500-750 F. is employed. The puffing is accomplished by the rapid transfer of heat from the rolls to the material to be puffed. Accordingly the material should be subjected to sufiicient pressure in the rolls to effect rapid heat transfer and to produce the resultant pufling. The pressure to be employed depends upon a large number of factors, included in which are the temperature of the rolls, the speed of the rolls, the moisture content of the pellets, the nature of the material being puffed, and the extent of pufiing desired. Usually sufficient pressure is employed to deform the material being puffed to some extent.

The material fed to the rolls may be at room temperature, but generally it is preferred to preheat the material. By preheating the material, the quantity of heat which must be supplied by the rolls is reduced and accordingly the capacity of a given piece of equipment can be substantially increased. Preheating is advantageous and it has been found desirable to heat the material to from 125-300 F. prior to the time it is fed to the rolls. In general preheat temperatures within the range 125- 175 F. are sufiicient.

One method of pre-heating the material which has been found satisfactory is the radiant heating of the pieces to be puffed as they advance along a conveyor and are fed to the rolls. It has been found that some materials may reach the point of incipient pulling at the point at which they are dropped into the nip of the rolls by elevating the temperature of the material to 150-300" F. At the temperatures and at the usual moisture levels employed for this operation the material is generally of a fairly plastic nature, and accordingly deforms readily in the rolls and takes up sufiicient heat to putt the material to a large volume. The amount of pressure which is applied to the material is not excessively great. Preferably the rolls are maintained out of contact to eliminate wear. Even where the rolls are separated by as much as A or more, the amount of pressure and heat applied to the material is sufiicient to effect satisfactory puffing.

Materials may be puffed between rolls which are rotating at this same peripheral speed as well as between rolls which have some differential in their peripheral speed. In general, the differential in the peripheral speed is not necessary, and accordingly it is preferred to operate with the rolls at the same peripheral speed. At temperatures of 700-750 F. peripheral speeds of 150-200 ft./min. have been found highly satisfactory.

The time period during which the material is subjected to heat and pressure in the rolls may be extremely small. Thus time periods as low as approximately 0.01 second have been found effective in this puffing operation. In general, time periods in excess of 1 second are usually not necessary.

Considerable variation is possible in various conditions as has been indicated above. In general, by means of this process it is possible to obtain volumes of from 700-2400 cc. per 100 g. of material.

Example I A dough was made up of the following ingredients in the following proportions by weight:

Parts Corn meal 25 Ground rolled o 75 Salt 3 dough was sheeted to a thickness of to ,4, and the sheet was then dried to about 16-18% moisture. The dried sheet was then cut into pieces which were run between rolls heated to about 400 F. The material readily puffed to a light weight product having a volume of about 1400 cc. per grams.

In Examples 2 to 6 the mixtures of materials indicated were subjected to the same processing described in Example 1, including the relative proportion of water. The products obtained were of the same general characteristics as the product of Example 1, differing according to the characteristics of the components of the mixture.

Example 2 Parts Ground rolled o 25 Corn meal 75 Salt 3 Example 3 Parts Ground r1ce 100 Salt 3 (dough cooked 1 /2 hours instead of 1 hour).

A dough was prepared from the following ingredients:

White corn con s b-- 9 Yellow corn cones 1b.... 1 Cocoa n7 4 Salt oz 5.1 Sugar oz 10.9 Water lb 5 The dough was cooked 1 hour 45 minutes in a jacketed mixer heated by steam at 20 pounds per square inch. The dough obtained was extruded into round pellets which were then dried at F. for 60 minutes. The dried pellets had a moisture content of about 13.0%.

The pellets were subjected to radiant heat while rolling down an incline toward the puffing rolls. The pellets reached a temperature approximating F. at the time they dropped from the end of the incline into the nip of the rolls. The pro-heated pellets then passed between a pair of rolls maintained at 550 F. In passing through the rolls, the pellets puffed to a volume of approximately 1200 cc. per 100 grams. The product had a final moisture content of about 6.8%.

In Examples 8 to 11 the doughs were made, cooked, extruded, and dried in the same manner as described in Example 7. The dried pellets were likewise subjected to the radiant pre-heat described in Example 7, and were sub ected to the same type of putting operation except that the rolls were at the temperatures indicated.

Example 8 Sorghum 10 lbs. 2 oz. Salt 5.1 oz. Sugar 10.9 oz. Water 5 lbs.

Moisture content of dried pellets- 13.7%

Roll temperature 550 F.

Volume of product 1200 cc. per 100 grams. Moisture content of final product 7.7%.

Example 9 Yellow corn cones 4 lbs. 8 oz. White rye flour 4 lbs. 8 oz. Oat flour 1 lb. Barley malt 3.2 oz. Salt 3.2 oz. Molasses 8 oz. Water lbs. Moisture content of dried pellets 13.6%. Temperature of rolls 550 F.

Example 10 White corn cones 7 lbs. Yellow corn cones 1 lb. Wheat bran 1 1b. Oat bran 11b. Salt 5.1 02. Sugar 10.9 oz. Water 5 lbs. Moisture content of dried pellets 13.2% Temperature of rolls 350 F. Volume of product 1000 cc. per 100 grams. Moisture content of final product- 6.7%.

Example 11 White corn cones 9 lbs. 102. Yellow corn cones 1 lb. 1 oz. Powdered milk 8 oz. Salt 5.1 oz. Sugar 10.9 oz. Water 5 lbs. Moisture content of dried pellets 13.7% Temperature of rolls 700 F Volume of product 1650 cc: per 100 grams. Moisture content of final product. 7.0%.

Example 12 Parts Wheat starch 91 Sucrose 6.2 Salt 2.8 Water 50 In Examples 13, 14, and 16 the materials listed therein were processed as described in Example 12. The products had characteristic flavors which permitted their use as snacks.

Example 13 Potato flour parts 7 White corn do 45 7 Sucrose do 5.8 Salt do 2.8 Water do 5.0 Volume of product cc 1000 Example 14 Tapioca flour ..parts 38 Wheat starch do 38 Salt do 3 Potato flour do 19 Water do Volume of product cc 940 Example 15 White corn parts 76 Yellow corn do 10 Cheddar cheese do 4 Salt do 2.5 Sugar do 5 Water .do 50 Volume of product cc 1080 Example 16 White corn parts 88.8 Salt do 2.7 Sugar do 5.5 Dried yeast do 3.0 Water do 5.0 Volume of produc 1200 Example 17 A dough was prepared from: Parts Tapioca flour 80 Cocoa 20 Salt 2.5 Water 50 The dough was cooked and extruded as described in the preceding examples. The pellets were dried to a moisture content of about 13%. The dried pellets were preheated to about 140 F. and then pulled between rolls heated to 700 F. The puffed product had a volume of about 1700 cc. per grams. The product was readily convertible into a pudding type dessert.

While in many of the preceding examples the product from the pulling rolls had a moisture content of from 6-7%, this may vary, depending upon the moisture content of the material being pulled. Following pulling it is usually desirable to dry the product down to 3% moisture to increase the stability and shelf life of the product. This, however, is unnecessary where the product is to be consumed in a short period of time and the shelf life and long term stability are not needed.

Any pair of rolls heated to the temperature range herein indicated may be employed for the production of the product. The rolls may have smooth surfaces, or may be corrugated or otherwise shaped. The rolls may be heated by direct gas firing either on the external or internal surface of the rolls. They may be heated by radiant heat or by high temperature fluid media such as the mixture of diphenyl and diphenyl oxide sold under the trademark Dowtherm.

I claim as my invention:

1. Process of pulling a cooked starch-containing dough product which comprises passing the cooked dough product between rolls heated to a temperature within the approximate range of 350800 F.

2. Process of puffing a cooked starch-containingdough product which comprises passing the cooked dough product between rolls heated to a temperature within the approximate range of 500750 F.

3. Process of producing a pulled product which comprises cooking a starch-containing dough, subdividing the cooked dough into small pieces, drying the small pieces to a moisture content within the approximate range of 8% to 18%, subjecting the dried pieces to heat and pressure by passing them between rolls heated to a temperature within the approximate range of 350-800 F.

4. Process of preparing a pulled product which comprises cooking a starch-containing dough, subdividing the cooked dough into small pieces, drying the small pieces to a moisture content within the approximate range of 8% to 18%, preheating the dried pieces to a temperature withinthe approximate range of -300 F., and then subjecting the preheated pieces to heated pressure by passing them between rolls heated to a temperature within the approximate range of 350-800 F. to pull the pieces.

5. Process of preparing a pulled product which comprises cooking a starch-containing dough, subdividing the cooked dough into small pieces, drying the small pieces to a moisture content within the approximate range of 8% to 18%, preheating the dried pieces to a temperature within the approximate range of 125-175 F., and then subjecting the preheated pieces to heated pressure by passing them between rolls heated to a temperature within the approximate range of 500750 F. to pull the pieces.

6. Process of preparing a pulled product which comprises cooking a starch-containing dough, subdividing the cooked dough into small pieces, drying the small pieces to a moisture content within the approximate range of 10% to 14%, preheating the dried pieces to a temperature within the approximate range of 125-175 F., and then subjecting the preheated pieces to heat and pressure by passing them between rolls heated to a temperature within the approximate range of 500-750 F. to pull the pieces.

7. Product produced according to claim 1.

8. Product produced according to claim 6.

References Cited in the file of this patent UNITED STATES PATENTS 1,832,813 Luke Nov. 17, 1931 1,925,267 McKay Sept. 5, 1933 2,131,450 McKay Sept. 27, 1938 

1. PROCESS OF PUFFING A COOKED STARCH-CONTAINING DOUGH PRODUCT WHICH COMPRISES PASSING THE COOKED DOUGH PRODUCT BETWEEN ROLLS HEATED TO A TEMPERATURE WITHIN THE APPROXIMATE RANGE OF 350-800*F. 